2/1 game forcing

2/1 game forcing ("Two-over-one game forcing") is a bidding system in modern contract bridge in which, after a one-level opening bid, a non-jump response in a new suit at the two level commits the partnership to bidding at least game.

Normal 2/1 game forcing auctions

The 2/1 auctions are 1Hearts–2Clubs, 1Hearts–2Diams, 1Spades–2Clubs, 1Spades–2Diams, and 1Spades–2Hearts. Hands without an opening bid (generally 12+ high card points) are required to respond 1NT to 1Spades, or to 1Hearts if they lack 4 spades.

Exceptions to 2/1 game force

Some pairs don't play that 1Diams–2Clubs is game forcing, although some do. Also, 2/1 game forcing doesn't apply to a passed hand, or if there is an intervening bid or double by an opponent. Some pairs play that 2/1 isn't absolutely game forcing; the pair can stop below game only when responder rebids his suit. For example, 1Hearts–2Clubs; 2Hearts–3Clubs is treated as nonforcing by some 2/1 players. A regular partnership should discuss this possibility.

1NT response forcing or semi-forcing for one round

Because the two-level responses are stronger than in Standard American bidding, the response of 1NT to 1Hearts or 1Spades opening is forcing for one round and is used (among other things) for weaker hands containing low-ranking suits. Since the 1NT response is forcing, hands with a three-card limit raise can start with 1NT and later jump-support partner. See Forcing notrump for additional details. Some pairs play a variant in which the 1NT response to 1Hearts or 1Spades is semi-forcing.

Other 2/1 features

Use of the 2/1 system usually implies (at least) the following additional agreements:
*Five card majors, i.e. major suit openings require at least a five-card suit;
*Limit raises of major suit openings, i.e. the jump raise 1Spades – 3Spades or 1Hearts – 3Hearts shows a game-invitational hand with at least four-card support (unless Bergen raises are used);
*Inverted minor raises, in which a jump raise of a minor suit opening is a weak preemptive bid, while a single raise is strong and forcing for one round;
*Jacoby transfers over 1NT opening;
*Jacoby 2NT, showing strong support with 4 or more cards;
*Splinter bids;
*New minor forcing;
*Fourth suit forcing and artificial.

Some also utilize Bergen raises.

Example sequences

1Spades – 2Clubs
2Diams – 2Spades
Forcing to game, with original spade support and good club suit. This is different from standard bidding, in which such a sequence would show about 10 points, and club suit could be semi-fake.

1Spades – 2Clubs
2Spades – 2NT.
Forcing to game, with balanced hand and a good club suit.

1Spades – 2Clubs
2Diams – 3Clubs
Forcing, unless the partnership has agreed that this is an exception to the "2/1 rule."

1Diams – 2Clubs
Forcing for one round only (as in Standard American), except in the variant of 2/1 where this sequence is game forcing as well.

1Clubs – 2Clubs
Forcing for one round; 10 points or more with at least four clubs.

1Clubs – 3Clubs
Weak; 9 points or less -- sometimes much less -- with at least five clubs.

1Hearts – 2Hearts
Weak; 6-9 points with at least 3 hearts (unless Bergen raises are in use, in which case it shows precisely 3 hearts)

1Spades – 1NT;
2Clubs – 2Spades
Shows a weak hand, 6-9 points, with precisely two spades. Some also use this for an extremely weak hand (0-5) with three spades.

1Spades – 1NT;
2Clubs – Pass
Shows a very weak hand, perhaps 5-7 points, with at least four clubs.

1Spades – 1NT;
2Clubs – 2Diams
Shows a weak hand, 5-9 points, with a long diamond suit.

1Spades – 1NT;
2Diams – 2Hearts
Shows a weak hand, 5-9 points, with a long heart suit.

1Spades – 1NT;
2Hearts – 3Clubs
Shows a weak hand, 5-9 points, with a long club suit.

1Spades – 1NT;
2Clubs – 2NT;
Shows 10-11 points without support for spades.

1Spades – 1NT;
2Clubs – 3Spades
Shows 10-11 points with 3-card support for spades.

1Spades – 3Spades
Shows 10-11 points with at least 4-card support for spades.

1Spades – 1NT;
2Clubs – 3Hearts
Shows 10-11 points with a long heart suit.

1Diams – 2Hearts
This is a jump response, and there are different ways of handling it. In Standard American, such a "jump shift" shows a very strong hand and is unequivocally forcing. However, since such hands do not occur with great frequency, it is more common today to use such a bid to show a weak hand with a long suit, unsuitable for defense. Another possibility is to play it as a "fit-showing jump", showing 8-10 points, a decent heart suit, and good diamond support.

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